The present invention relates to projection screens, and in particular to improved reflective elements which form the surface of the screen.
Projection screens have been developed which employ the dull side of compression rolled aluminum foil as the reflective element. The screens have improved reflective properties relative to the beaded and lenticular screens which have been standard, and are now used in double curved screens in place of beaded or lenticular reflective screens. Also, screens with compound curvature have been developed using such foil reflective elements which focus the reflected image in a predesignated area and reject outside light to a degree that the screens can often be used in the daytime, as illustrated in the patent to Chandler, U.S. Pat. No. 3,408,132. If ambient light is high, such screens can be used in the daytime with a high-power projector, and with a relatively low-power projector when excessive ambient light is not present. In such screens the irregular surface of the reflective foil provides the foil material with high gain to protect the image in the predesignated area spreading the image uniformly throughout that area.
A primary difficulty with compression rolled aluminum foil screens is that the irregular surface of the screen which provides its high gain can quite easily be scratched or otherwise damaged. The reflective surface of such screens is exposed and is extremely fragile, ane even minor contact with the screen can damage it so that the image projected thereon is impaired. As a result, the utility of such screens is limited even through their advantages are well known.
A primary usage of known aluminum foil screens is in the large screen projection television systems which are now becoming quite popular. Many of such television systems utilize a relatively small television receiver, the picture from which is projected by a lens and in some cases employing various mirrors onto a large projection screen of the aluminum foil type.
Both the advantages and inherent difficulties in using the aluminum foil screens described above become readily apparent when such screens are used in a television projection system. The advantage of such as screen is that a sufficiently bright picture is provided even though the projection system has relatively little power as long as the room in which the device is located is kept sufficiently dark. However, the gain of the device is insufficient to permit ready viewing of the projected image in areas with high ambient light. A further difficulty with such screens is that in a home environment, the likelihood that the screens will be permanently damaged is extremely high. Television projection systems using this type of screen are ordinarily supplied with instructions and warnings as to the fragility of the screen, and a camels hair dusting brush is recommended so that some effort can be made to clean the screen. The reflective properties of the screen are impaired by accumulations of cigarette smoke, cooking oils, fingerprints, and other deposits, and cannot be readily removed without damaging the screen. The likelihood that the screen will still be damaged in a home environment is quite high, and the useful life of such a screen in a home environment is quite limited.